Greetings Frank,
What you have described in your design rules sounds perfectly
reasonable. I have some recommendations concerning the source, material
and the tooling. I take it that the ribbon connectors are ZIF type. If
that is the case, the profile tolerance of the ZIF termination contact
area (which must have a thickness of approximately 0.020) must be
+/-.004 TP, which must be noted on the drawing. This imposes a conflict
with the typical manufacturing process of steel rule die cut outlines
(as opposed to a routed edge in rigid fabrication) typical in flex
fabrication, which is +/-.010. The solution is to use "Hard Tooling" in
the ZIF area. This is typically poses a further investment by the
customer with most shops. AllFlex, however, has a very wide selection of
hard tooling just for the ZIF application. Contact Larry Smith or Paul
Kopnick of AllFlex (507) 633-7162. I also recommend that you use 1 oz CU
on 1 mil polyimide (Kapton) with a 1 mil polyimide and 1 mil acrylic
adhesive cover layer. Remember to define the cover layer "hold-back"
distance that exposes the ZIF connector fingers. Polyimide is
recommended for its flexibility, low cost and high reliability. I also
recommend that the exposed fingers be either HASL or gold. My preference
is gold, but a few cents can be saved with HASL (which is the way LXE
tends to lean). I can send a PADS PowerPCB file to you (or any other
interested subscriber) that you can use as a boilerplate if you are
interested. Just drop me a line, offline.


Chris Taylor
Senior PC Designer
LXE, Inc.
125 Technology Pkwy
Norcross, GA 30092
e-mail: [log in to unmask]
(770) 447-4224 X3242 Voice
(770) 447-6928 FAX



>----------
>From:  Frank Frank[SMTP:[log in to unmask]]
>Sent:  Monday, July 06, 1998 11:00 PM
>To:    [log in to unmask]
>Subject:       [DC] Flex circuits
>
>Needs some help on flex circuit design.  It has been a long time since my
>last flex circuit, and I am looking for some input to good fabrication
>facilities as well as reasonable spacing and width specs to expect.  Any
>input would be appreciated.
>
>In particular, I am looking at a ribbon connector type arrangement
>(straight pin to pin connections) with trace widths in the 8-10 mil range
>and pad clearances as small as .012 mil.......   Does this sound like
>something some of you are already doing?  I'm looking at a product that
>will run in the 50-100 lot per month quantities.
>
>Thanks in advance for any input.
>
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